<!DOCTYPE html>
<html>
	<head>
	<!-- 外边距 -->
		<meta charset="UTF-8">
		<title>Insert title here</title>
		<style type="text/css">
			#big{
				width:200px;
				height:200px;
				background-color: green;
				overflow:hidden;/* 解决粘连问题 */
			}
			#small{
				width:50px;
				height:50px;
				background-color: blue;
				margin-top: 30px;
				margin-left: 50px;
			}
		</style>
	</head>
	<body>
		<div id="big">
			<div id="small"></div>
		</div>
	</body>
</html>